page_title: List of unusual units of measurement
section_title: Proof: alcohol concentration
hierarchical_section_title: List of unusual units of measurement / Other / Proof: alcohol concentration
caption_attribution_description: A mostly-empty bottle of Bacardi 151 pictured with cap and shotglass. Notice the metallic flame arrester on the spout.
context_page_description: An unusual unit of measurement is a unit of measurement that does not form part of a coherent system of measurement; especially because its exact quantity may not be well known or that it may be an inconvenient multiple or fraction of a base units.
  This definition is not exact since it includes units such as the week or the light-year, which are quite "usual" in the sense that they are often used but which can be "unusual" if taken out of their common context, as demonstrated by the furlong-firkin-fortnight system of units.
  Many of the unusual units of measurements listed here are colloquial measurements, units devised to compare a measurement to common and familiar objects.
context_section_description: Up to the 20th century, alcoholic spirits were assessed in the UK by mixing with gunpowder and testing the mixture to see whether it would still burn; spirit that just passed the test was said to be at 100° proof. The UK now uses percentage alcohol by volume at 20 °C (68 °F), where spirit at 100° proof is approximately 57.15% ABV; the US uses a "proof number" of twice the ABV at 60 °F (15.5 °C).
caption: A (nearly empty) bottle of 151° proof rum
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